CD 4 + CD 25 high forkhead box protein 3 + regulatory T lymphocytes suppress interferon‐γ and CD 107 expression in CD 4 + and CD 8 + T cells from tuberculous pleural effusions

Summary Tuberculous pleural effusion is characterized by a T helper type 1 ( T h1) profile, but an excessive T h1 response may also cause tissue damage that might be controlled by regulatory mechanisms. In the current study we investigated the role of regulatory T cells ( T reg ) in the modulation of T h1 responses in patients with tuberculous ( TB ) pleurisy. Using flow cytometry we evaluated the proportion of T reg ( CD 4 + CD 25 high forkhead box protein 3 + ), interferon ( IFN)‐ γ and interleukin ( IL )‐10 expression and CD 107 degranulation in peripheral blood ( PB ) and pleural fluid ( PF ) from patients with TB pleurisy. We demonstrated that the proportion of CD 4 + CD 25 + , CD 4 + CD 25 high F oxP3 + and CD 8 + CD 25 + cells were increased in PF compared to PB samples. M ycobacterium tuberculosis stimulation increased the proportion of CD 4 + CD 25 low/neg IL ‐10 + in PB and CD 4 + CD 25 low/neg IFN‐ γ + in PF ; meanwhile, CD 25 high mainly expressed IL ‐10 in both compartments. A high proportion of CD 4 + CD 107 + and CD 8 + CD 107 + cells was observed in PF . T reg depletion enhanced the in‐vitro M . tuberculosis ‐induced IFN‐ γ and CD 4 + and CD 8 + degranulation responses and decreased CD 4 + IL ‐10 + cells in PF . Our results demonstrated that in TB pleurisy T reg cells effectively inhibit not only IFN‐ γ expression but also the ability of CD 4 + and CD 8 + cells to degranulate in response to M . tuberculosis .